Power distribution area voltage imbalance treatment method and system based on phase-change switch and SVG (static var generator)

Abstract

The invention discloses a power distribution area voltage imbalance treatment method and system based on a phase-change switch and an SVG. The method comprises the steps that firstly, a power distribution network full-node voltage imbalance optimization multi-objective function and a phase-change switch phase sequence and SVG compensation instruction current optimization model are established; calculating a node three-phase voltage by adopting a three-phase unbalanced load flow, and optimizing the obtained phase-change switch phase sequence and SVG compensation instruction current optimization model by using a fast non-dominated sorting genetic algorithm to obtain a Pareto leading solution set of phase-change switch phase sequence optimization and SVG negative sequence compensation current; screening the obtained Pareto leading-edge solution set, and selecting a result which not only meets the national standard but also can reduce the commutation frequency of the commutation switch and the negative sequence compensation current of the SVG as an optimal instruction; according to the obtained optimal instruction, a commutation instruction and a compensation current instruction are issued to a commutation switch and an SVG in the power distribution network respectively, and comprehensive treatment of the voltage unbalance of all nodes of the power distribution network is achieved.

Description

Background Art

[0002] Most of the power users in the low-voltage distribution network are single-phase loads. Due to the large number of distributed power sources in the low-voltage distribution network and the development of diversified household appliances, there is a large uncertainty in the source and load in the distribution network, resulting in three-phase imbalance in the distribution area. Three-phase imbalance will increase the loss of the distribution network and reduce the operating efficiency of power equipment. The current imbalance management methods for low-voltage distribution networks include phase sequence optimization and active compensation. The phase sequence optimization method adjusts the phase sequence of the single-phase load connected to the three-phase line to make the three-phase load close to achieve the purpose of imbalance management. Phase sequence optimization can be divided into manual phase adjustment and intelligent phase adjustment. Manual phase adjustment is time-consuming and labor-intensive, and it cannot be adjusted online according to the real-time load situation in the area. Intelligent phase switching refers to the use of optimization algorithms to reasonably calculate the phase switching instructions, and then send the phase switching information to the phase switching switch composed of power electronic devices to achieve online real-time management of three-phase imbalance. Active compensation uses power quality management equipment such as static var generators (SVG) to compensate for unbalanced currents.

[0003] The current mainstream intelligent phase sequence optimization method only considers the three-phase current imbalance on the outlet side of the low-voltage distribution transformer, and fails to consider the three-phase voltage imbalance at each node in the substation. The node voltage imbalance management effect in the substation cannot be guaranteed. At the same time, its phase sequence optimization result is related to the current single-phase load in the substation. There may be a situation where the imbalance management cannot be achieved no matter how the phase sequence is optimized, which affects the management effect. In addition, the single-phase load phase sequence switching to adjust the user's load current is not a simple phase-to-phase transfer, and the redistribution of the power flow after the network architecture must be considered, which is not taken into account by the current mainstream intelligent phase sequence optimization method. Although the traditional point-to-point nearby compensation strategy of the active compensation scheme can achieve effective management of imbalance, the management cost is greatly increased. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method and system for voltage imbalance management in a distribution station area based on phase-changing switches and SVG in response to the deficiencies in the above-mentioned prior art, so as to solve the technical problems that traditional phase-changing switch control strategies cannot achieve voltage imbalance management at all nodes of the distribution system and that phase-changing switches and SVG multi-type resources cannot be efficiently coordinated and controlled, so as to achieve comprehensive management of voltage imbalance at multiple nodes within the station area.

[0005] The present invention adopts the following technical solutions: The method for controlling voltage imbalance in a distribution station area based on a phase-changing switch and SVG includes the following steps: S1. Obtain the topology of the distribution network, line impedance data, data of each node, phase-changing switch and SVG data; S2. According to the topology of the distribution network, the line impedance data, the data of each node, the phase-changing switch and the SVG data obtained in step S1, a multi-objective function for optimizing the voltage imbalance of all nodes in the distribution network and an optimization model for the phase sequence of the phase-changing switch and the SVG compensation instruction current are established; S3, using the three-phase unbalanced power flow to calculate the node three-phase voltage, using the fast non-dominated sorting genetic algorithm to optimize the commutation switch phase sequence and SVG compensation command current optimization model obtained in step S2, and obtain the Pareto frontier solution set of the commutation switch phase sequence optimization and SVG negative sequence compensation current; S4, screening the Pareto front solution set obtained in step S3, and selecting the result that not only meets the national standard but also reduces the number of commutation times of the commutation switch and the negative sequence compensation current of the SVG as the optimal instruction; S5. According to the optimal instruction obtained in step S4, a commutation instruction and a compensation current instruction are respectively issued to the commutation switches and SVG in the distribution network to achieve comprehensive management of voltage imbalance at all nodes in the distribution network.

[0006] Preferably, in step S1, the distribution network topology includes a three-phase network topology structure; the three-phase line impedance data includes the three-phase line impedance of adjacent nodes; the data of each node includes the load power of each node, the voltage amplitude and phase angle data of each node; the phase-changing switch data includes the current phase-changing switch access phase sequence; the SVG data includes the rated capacity of each SVG and the current output negative sequence current; Order positive sequence, negative sequence, zero sequence node admittance matrix , , .

[0007] Preferably, step S2 specifically includes: S201. Determine the target of comprehensive management of three-phase imbalance in distribution network as negative sequence voltage imbalance of each node <2%; S202. Construct a multi-objective function for optimizing voltage imbalance at all nodes of the distribution network and an optimization model for the phase sequence of the phase-changing switch and the SVG compensation instruction current, with the optimization objectives of minimizing the sum of the negative-sequence voltage imbalance at all nodes, minimizing the number of phase changes, and minimizing the sum of the negative-sequence compensation current amplitudes output by SVG; constraints include maintaining the three-phase voltage at the distribution network node within the range specified by the national standard, the number of continuous operations of a single phase-changing switch not exceeding the specified upper limit, and the negative-sequence current output by SVG not exceeding the rated capacity; the control variables are the phase sequence of the phase-changing switch and the negative-sequence compensation current output by SVG.

[0008] Preferably, the multi-objective function for optimizing voltage imbalance at all nodes of the distribution network includes: Total negative sequence voltage unbalance objective function:

[0009] in, is the node number, is the number of network nodes, For Node The negative sequence voltage unbalance degree, For Node m The negative sequence voltage, For Node m The positive sequence voltage; SVG total output capacity objective function:

[0010] in, k Number the SVG. K is the total number of SVGs, is the output negative sequence current of the kth SVG; Commutation times objective function:

[0011] in, It is the total number of commutation times of the commutation switch compared to the current phase sequence.

[0012] Preferably, the node voltage constraints are as follows:

[0013] in, is the minimum node voltage, is the maximum value of the node voltage; Each phase-changing switch sets a maximum number of continuous phase-changing times. If a phase-changing switch operates continuously for more than the specified value, the current phase sequence will remain unchanged during the next phase-changing. The action constraints are as follows:

[0014] in, For the p The number of consecutive commutation times of a commutation switch, For the p The maximum number of continuous commutation times of a phase-changing switch.

[0015] Preferably, in step S3, the three-phase unbalanced power flow and the fast non-dominated sorting genetic algorithm NSGA-II are applied to solve the multi-objective optimization model, and the multi-node voltage unbalance optimization model and the three objective functions of the model are solved; through multiple iterative optimizations of the NSGA-Ⅱ genetic algorithm, a set of Pareto optimal solution sets are obtained, and the objective function of the Pareto optimal solution set is equivalent to the Pareto optimal frontier of total negative sequence voltage imbalance, number of commutation times and total output capacity of SVG.

[0016] Preferably, the NSGA-II algorithm is used to solve the multi-objective optimization problem established in step S2 as follows: S3021, generating an initial population of the genetic algorithm, the population size is POP, and a single individual includes the phase sequence of the phase-changing switch and the negative sequence current output by the SVG; S3022, calculating three individual objective functions, the total voltage unbalance objective function needs to be obtained through the unbalanced power flow calculation result; S3023, non-dominated sorting and crowding analysis, non-dominated sorting and crowding calculation are performed on all individuals in the population, and the priority and ranking of individuals in the population are determined through the three fitness functions of the individuals. Secondly, the crowding is calculated and the individuals at the same level are sorted to prevent the algorithm from falling into the local optimum. Retaining individuals with high crowding is conducive to population diversity; S3024. Selecting parents suitable for reproduction based on the tournament selection method and placing them into a mating pool, wherein the number of individuals in the mating pool is half of the initial population; S3025. Randomly select a parent generation in the mating pool, perform crossover and genetic operations, and generate offspring individuals; S3026, merge the parent population and the child population to obtain a merged population, perform non-dominated sorting and crowding calculation on the merged population based on the elite selection strategy, and generate a new population with the top-ranked POP individuals; S3027. Determine whether to stop iteration based on the objective function of each individual in the new population, the number of iterations and other convergence conditions. If iteration is not stopped, perform selection, crossover and mutation operations on the population to generate the next generation population and enter step S302. If the convergence conditions are met, output the Pareto optimal solution set.

[0017] Preferably, in step S3021, the total voltage unbalance objective function is obtained through the unbalanced power flow calculation result, which is specifically as follows: S30221, set the initial value of node positive sequence, negative sequence and zero sequence voltage , , , the positive sequence voltage amplitude is 1.0pu, the negative sequence and zero sequence voltage amplitudes are 0, and the initial values ​​of the node three-phase voltages are calculated , , ; S30222, based on node injection power , , , update the node injection three-phase current, and based on the symmetrical component method, calculate the node injection positive sequence, negative sequence, and zero sequence current in the updated network , , ; S30223, the positive sequence network is an active network, and the forward-backward method is used to solve the node positive sequence voltage , the negative sequence network and the zero sequence network are passive networks, and the node voltage equation is used to obtain , , t is the number of iterations; S30224, generate node three-phase voltage , , ; S30225, determine whether it has converged or reached the maximum number of iterations, if not converged or not reached the maximum number of iterations, update t=t+ 1. Start the next iteration from step S30222.

[0018] Preferably, in step S4, firstly, a feasible solution that meets the standard in the Pareto optimal solution set obtained in step S3 is screened, and after taking the commutation switch phase sequence optimization instruction and the SVG output negative sequence current instruction represented by the feasible solution, the voltage imbalance degree of all nodes in the local distribution network meets the national standard requirements; Then, a non-dominated sorting is completed again among the remaining feasible solutions, and the optimal compromise solution with low commutation times and small total SVG output capacity is selected as the commutation switch phase sequence optimization instruction and SVG output negative sequence current instruction.

[0019] In a second aspect, an embodiment of the present invention provides a system for managing voltage imbalance in a distribution station area based on a phase-changing switch and an SVG, comprising: Data module, which obtains the topology of the distribution network, line impedance data, data of each node, phase-changing switch and SVG data; The construction module establishes a multi-objective function for optimizing voltage imbalance at all nodes of the distribution network and an optimization model for the phase sequence of the commutation switch and the compensation command current of the SVG based on the obtained distribution network topology, line impedance data, data of each node, commutation switch and SVG data; The optimization module uses the three-phase unbalanced power flow to calculate the three-phase voltage of the node, and uses the fast non-dominated sorting genetic algorithm to optimize the obtained commutation switch phase sequence and SVG compensation command current optimization model to obtain the Pareto frontier solution set of the commutation switch phase sequence optimization and SVG negative sequence compensation current; The screening module screens the obtained Pareto front solution set and selects the result that not only meets the national standard but also reduces the number of commutation switches and the negative sequence compensation current of SVG as the optimal instruction; The output module, based on the obtained optimal instructions, sends commutation instructions and compensation current instructions to the commutation switches and SVG in the distribution network respectively, to achieve comprehensive management of voltage imbalance at all nodes in the distribution network.

[0020] In a third aspect, a computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method for controlling voltage imbalance in a distribution station area based on phase-changing switches and SVG when executing the computer program.

[0021] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, including a computer program, which, when executed by a processor, implements the steps of the above-mentioned method for controlling voltage imbalance in a distribution station area based on phase-changing switches and SVG.

[0022] In a fifth aspect, a chip includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method for controlling voltage imbalance in a distribution station area based on phase-changing switches and SVG when executing the computer program.

[0023] In a sixth aspect, an embodiment of the present invention provides an electronic device, including a computer program, which, when executed by the electronic device, implements the steps of the above-mentioned method for controlling voltage imbalance in a distribution station area based on phase-changing switches and SVG.

[0024] Compared with the prior art, the present invention has at least the following beneficial effects: A method for controlling voltage imbalance in a distribution station area based on phase-changing switches and SVG. The method uses phase-changing switches and SVG as control equipment, comprehensively considers the three-phase voltage imbalance of all nodes in the local distribution network as the control target, and can achieve efficient control of voltage imbalance at all nodes compared to traditional phase-changing switch control schemes, and is not limited to the suppression of current imbalance on the low-voltage side of the transformer. The method is based on the voltage imbalance calculated based on the three-phase unbalanced power flow, and considers the influence of the phase-changing switch action on the network power flow reconstruction, so as to better reflect the actual operating state of the distribution network. The present invention adopts a fast non-dominated sorting genetic algorithm to solve the model, so as to achieve efficient optimization of the phase sequence instructions of the phase-changing switch and the optimal compensation instructions of the SVG.

[0025] Furthermore, step S1 obtains the local distribution network topology, line impedance data and node data to support unbalanced power flow calculation, obtains the data of phase-changing switches and SVG, and supports the fast non-dominated genetic algorithm to optimize the optimal instructions of phase-changing switches and SVG. The above data are the data basis for the implementation of this method.

[0026] Furthermore, step S2 takes the minimum sum of all-node negative sequence voltage imbalance, the minimum number of commutation times, and the minimum sum of SVG output negative sequence compensation current amplitudes as optimization objectives, while considering the constraint characteristics of the commutation switch and the SVG, and taking the phase sequence switching of the commutation switch and the output compensation current of the SVG as control variables. By constructing a multi-objective function optimization mathematical model, it serves as the basis for solving the subsequent steps.

[0027] Furthermore, three objective functions, namely, total negative sequence voltage imbalance, total SVG output capacity, and number of commutation times, are constructed as optimization targets of the NSGA-II algorithm. Taking into account the governance effect, optimization of governance equipment capacity, and limitation of the number of actions, the governance effect is ensured to be achieved at a relatively low governance cost.

[0028] Furthermore, by setting node voltage constraints, it is ensured that the voltage of the distribution system after optimization by this method operates within a reasonable range. By setting a limit on the number of continuous actions of a single phase-changing switch, it is ensured that the single machine will not act frequently, thereby extending its service life.

[0029] Furthermore, step S3 adopts a fast non-dominated sorting genetic algorithm to achieve efficient solution of the optimization problem in view of the characteristics of the mixed integer programming problem of the multi-objective function optimization model constructed by the method; for the objective function of the sum of the negative sequence voltage imbalance of all nodes, the node voltage data is obtained through unbalanced power flow calculation to realize the calculation of the objective function.

[0030] Furthermore, the present invention adopts the NSGA-Ⅱ algorithm to update the offspring population through an elite selection strategy based on non-dominated sorting and crowding analysis, thereby preventing the population from converging to a local optimum, so as to achieve a rapid solution to the optimization problem and improve the optimization efficiency; through operations based on the tournament selection method and crossover and mutation, it helps to explore a wider solution space and improve the algorithm convergence speed to achieve a rapid solution to the optimization problem.

[0031] Furthermore, the unbalanced power flow can realize the accurate calculation of the three-phase voltage distribution of the local distribution network, accurately reflect the operating status of the distribution network after the phase-changing switch action and the SVG injection current update, thereby realizing the accurate solution of the total voltage imbalance objective function and ensuring the effectiveness and accuracy of this method.

[0032] Furthermore, step S4 selects the optimal solution from the Pareto solution set, and on this basis selects a compromise solution with the minimum number of commutation times and a smaller SVG output capacity, thereby avoiding the problem of insignificant improvement in the management effect of excessive commutation switches. At the same time, considering the SVG capacity, effective management of system voltage imbalance is achieved at a lower management cost.

[0033] It can be understood that the beneficial effects of the second to sixth aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0034] In summary, the present invention optimizes the phase sequence of the phase-changing switches and the negative-sequence output current of the SVG in the distribution network, thereby managing the imbalance from the load side and combining the advantages of active compensation and fine compensation to achieve comprehensive and efficient management of voltage imbalance at all nodes in the distribution network.

[0035] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0037] Figure 1 It is a flow chart of the process of the treatment method of the present invention; Figure 2 This is a flow chart of the fast non-dominated sorting genetic algorithm of the present invention; Figure 3 This is a flow chart of the three-phase unbalanced power flow algorithm adopted by the present invention; Figure 4 It is the topological diagram of low voltage distribution network; Figure 5 The histogram of negative sequence voltage imbalance at each node in the distribution network before the method is used; Figure 6 is a schematic diagram of the Pareto optimal solution set; Figure 7 This is a histogram of negative sequence voltage imbalance at each node in the distribution network after the method is used; Figure 8 A schematic diagram of a computer device provided by an embodiment of the present invention; Fig. 9 The present invention is a block diagram of an electronic device provided according to an embodiment. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0040] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0041] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0042] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0043] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0044] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0045] The present invention provides a method for controlling voltage imbalance in a distribution station area based on phase-changing switches and SVG, with the goal of comprehensively controlling voltage imbalance in a regional distribution network containing a large number of single-phase loads. By optimizing the phase sequence of the phase-changing switches installed in the network and optimizing the output negative-sequence compensation current instructions of the SVG, the method can reduce the number of phase changes and the total output capacity of the SVG as much as possible while taking into account the control effect of the voltage imbalance in the distribution network. The control scheme has good practical value and economic benefits.

[0046] Example 1 See also Figure 1 The present invention provides a method for controlling voltage imbalance in a distribution station area based on a phase-changing switch and SVG, comprising the following steps: S1. Obtain the topology of the distribution network, line impedance data, data of each node, phase-changing switch and SVG data; The distribution network topology is obtained, including the three-phase topology of the network. The three-phase line impedance data includes the three-phase line impedance of adjacent nodes. The data of each node includes the load power of each node, the voltage amplitude and phase angle data of each node. The phase-changing switch data and SVG data are obtained. The phase-changing switch data includes the current phase sequence of the phase-changing switch. The SVG data includes the rated capacity of each SVG and the current output negative sequence current.

[0047] Based on the acquired data, Order positive sequence, negative sequence, zero sequence node admittance matrix , , .

[0048] S2, based on the establishment of a multi-objective function for optimizing voltage imbalance at all nodes of the distribution network and a current optimization model for commutation switch phase sequence and SVG compensation command; S201. Determine the management objectives of comprehensive management of three-phase imbalance in distribution network; The control target is formulated according to the national standard GB / T 15543-2008 "Three-phase voltage imbalance of power quality" for voltage imbalance requirements during normal operation of the power grid. The control target in the present invention is not lower than the standard in the above national standard. The specific control target is that the negative sequence voltage imbalance degree of each node is <2%, as follows:

[0049] in, m Represents the network node number, Represents the node voltage negative sequence imbalance, Representative Node m Negative sequence voltage, Representative Node m Positive sequence voltage.

[0050] S202. Construct a multi-objective function for optimizing voltage imbalance at all nodes of the distribution network and an optimization model for the phase sequence of the phase-changing switch and the SVG compensation instruction current, with the optimization objectives of minimizing the sum of the negative-sequence voltage imbalance at all nodes, minimizing the number of phase changes, and minimizing the sum of the negative-sequence compensation current amplitudes output by SVG; constraints include maintaining the three-phase voltage at the distribution network node within the range specified by the national standard, the number of continuous operations of a single phase-changing switch not exceeding the specified upper limit, and the negative-sequence current output by SVG not exceeding the rated capacity; the control variables are the phase sequence of the phase-changing switch and the negative-sequence compensation current output by SVG.

[0051] The total negative sequence voltage unbalance objective function is as follows:

[0052] in, is the node number, is the number of network nodes, For Node The negative sequence voltage unbalance degree is calculated as follows: , For Node m The negative sequence voltage, For Node m The positive sequence voltage.

[0053] The objective function of SVG total output capacity is as follows:

[0054] in, k Number the SVG. K is the total number of SVGs, is the output negative sequence current of the kth SVG; The objective function of commutation times is as follows:

[0055] Wherein, N is the total number of commutation times of the commutation switch compared to the current phase sequence.

[0056] When performing commutation operation, the voltage of the node with a large load may change greatly and exceed the constraint range. Therefore, the node voltage constraint conditions are established as follows:

[0057] in, is the minimum node voltage, is the maximum node voltage.

[0058] In order to avoid the reduction of service life due to multiple continuous actions of the phase-changing switch, the maximum number of continuous phase-changing times is set for each phase-changing switch. If the number of continuous actions of a phase-changing switch exceeds the specified value, the current phase sequence will remain unchanged during the next phase-changing. The action constraints are as follows:

[0059] in, For the p The number of consecutive commutation times of a commutation switch, For the p The maximum number of continuous commutation times of a phase-changing switch.

[0060] S3, using three-phase unbalanced power flow to calculate the node three-phase voltage, using fast non-dominated sorting genetic algorithm (NSGA-Ⅱ) to find the optimal solution, and obtain the Pareto frontier solution set of commutation switch phase sequence optimization and SVG negative sequence compensation current; S301, applying the three-phase unbalanced power flow and the fast non-dominated sorting genetic algorithm NSGA-II to solve the multi-objective optimization model, and solving the multi-node voltage unbalance optimization model and the three objective functions of the model; S302. Through multiple iterations of optimization using the NSGA-Ⅱ genetic algorithm, a set of Pareto optimal solutions is obtained. The objective function of the Pareto optimal solution set is equivalent to the Pareto optimal frontier of total negative sequence voltage imbalance, number of commutation times, and total output capacity of SVG.

[0061] See also Figure 2 , the NSGA-Ⅱ algorithm is used to solve the multi-objective optimization problem established in step S2 as follows: S3021, generating an initial population of the genetic algorithm, the population size is POP, and a single individual includes the phase sequence of the phase-changing switch and the negative sequence current output by the SVG; S3022, calculate three individual objective functions. Among them, the total voltage unbalance objective function needs to be obtained through the unbalanced power flow calculation results; See also Figure 3 , the specific steps are as follows: S30221, set the initial value of node positive sequence, negative sequence and zero sequence voltage , , , the positive sequence voltage amplitude is 1.0pu, the negative sequence and zero sequence voltage amplitudes are 0, and the initial values ​​of the node three-phase voltages are calculated , , ; S30222, based on node injection power , , , update the node injection three-phase current, and based on the symmetrical component method, calculate the node injection positive sequence, negative sequence, and zero sequence current in the updated network , , ;

[0062] in, , , The three-phase current vector injected by the representative node.

[0063] S30223. Calculate the node voltage in the network: The positive sequence network is an active network, and the forward and backward method is used to solve the node positive sequence voltage , the negative sequence network and the zero sequence network are passive networks, and the node voltage equation is used to obtain , , t is the number of iterations; S30224, generate node three-phase voltage , , ; S30225, determine whether it has converged or reached the maximum number of iterations, if not converged or not reached the maximum number of iterations, update t=t+ 1. Start the next iteration from step S30222.

[0064] S3023, non-dominated sorting and crowding analysis, non-dominated sorting and crowding calculation are performed on all individuals in the population, and the priority and ranking of individuals in the population are determined through the three fitness functions of the individuals. Secondly, the crowding is calculated and the individuals at the same level are sorted to prevent the algorithm from falling into the local optimum. Retaining individuals with high crowding is conducive to population diversity; S3024. Selecting parents suitable for reproduction based on the tournament selection method and placing them into a mating pool, wherein the number of individuals in the mating pool is half of the initial population; S3025. Randomly select a parent generation in the mating pool, perform crossover and genetic operations, and generate offspring individuals; S3026, merge the parent population and the child population to obtain a merged population, perform non-dominated sorting and crowding calculation on the merged population based on the elite selection strategy, and generate a new population with the top-ranked POP individuals; S3027. Determine whether to stop iteration based on the objective function of each individual in the new population, the number of iterations and other convergence conditions. If iteration is not stopped, perform selection, crossover and mutation operations on the population to generate the next generation population and enter step S302. If the convergence conditions are met, output the Pareto optimal solution set.

[0065] Through multiple iterations of optimization using the NSGA-Ⅱ genetic algorithm, a set of Pareto optimal solutions is obtained, the objective function of which is equivalent to the Pareto optimal frontier of total negative sequence voltage imbalance, number of commutation times, and total output capacity of SVG.

[0066] S4, screening the obtained Pareto front solution set, and selecting the result that not only meets the national standard but also reduces the number of commutation times of the commutation switch and the negative sequence compensation current of the SVG as the optimal instruction; Step S4 describes how to screen the obtained Pareto solution set and select the result that meets the national standard and can reduce the number of commutation times of the commutation switch and the negative sequence compensation current of the SVG as the optimal instruction.

[0067] Specifically, firstly, the feasible solutions that meet the standards in the Pareto optimal solution set obtained in step S3 are screened, and after taking the commutation switch phase sequence optimization instructions and the SVG output negative sequence current instructions represented by the feasible solutions, the voltage imbalance degree of all nodes in the local distribution network meets the national standard requirements; Then, a non-dominated sorting is completed again in the remaining feasible solutions, and the optimal compromise solution with low commutation times and small total SVG output capacity is selected as the commutation switch phase sequence optimization instruction and SVG output negative sequence current instruction.

[0068] After the optimization instructions represented by the feasible solution set complete the management of the regional distribution network system, the voltage imbalance of all nodes in the system must meet the national standard requirements, as follows:

[0069] S5. According to the obtained optimal instructions, phase change instructions and compensation current instructions are respectively issued to the phase change switches and SVG in the distribution network to achieve comprehensive management of voltage imbalance at all nodes in the distribution network.

[0070] According to the obtained optimal instructions, the commutation instructions and compensation current instructions are respectively issued to the commutation switches and SVG in the distribution network, so as to realize multi-node comprehensive compensation for the voltage imbalance problem in the system.

[0071] It will be appreciated by those skilled in the art that various aspects of the present invention may be implemented as systems, methods or program products. Therefore, various aspects of the present invention may be specifically implemented in the following forms, namely: complete hardware implementation, complete software implementation (including firmware, microcode, etc.), or a combination of hardware and software implementations, which may be collectively referred to herein as "circuits", "modules" or "platforms".

[0072] Example 2 The present invention provides a distribution station area voltage unbalance management system based on phase-changing switches and SVG. The system can be used to implement the above-mentioned distribution station area voltage unbalance management method based on phase-changing switches and SVG. Specifically, the distribution station area voltage unbalance management system based on phase-changing switches and SVG includes a data module, a construction module, an optimization module, a screening module and an output module.

[0073] Among them, the data module obtains the topology of the distribution network, line impedance data, data of each node, phase-changing switch and SVG data; The construction module establishes a multi-objective function for optimizing voltage imbalance at all nodes of the distribution network and an optimization model for the phase sequence of the commutation switch and the compensation command current of the SVG based on the obtained distribution network topology, line impedance data, data of each node, commutation switch and SVG data; The optimization module uses the three-phase unbalanced power flow to calculate the three-phase voltage of the node, and uses the fast non-dominated sorting genetic algorithm to optimize the obtained commutation switch phase sequence and SVG compensation command current optimization model to obtain the Pareto frontier solution set of the commutation switch phase sequence optimization and SVG negative sequence compensation current; The screening module screens the obtained Pareto front solution set and selects the result that not only meets the national standard but also reduces the number of commutation switches and the negative sequence compensation current of SVG as the optimal instruction; The output module, based on the obtained optimal instructions, sends commutation instructions and compensation current instructions to the commutation switches and SVG in the distribution network respectively, to achieve comprehensive management of voltage imbalance at all nodes in the distribution network.

[0074] Example 3 The present invention provides a terminal device, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, graphics processors (GPU), tensor processors (TPU), digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions to implement the corresponding method flow or corresponding function; the processor described in the embodiment of the present invention can be used for the operation of the voltage imbalance control method of the distribution station area based on the phase-changing switch and SVG, including: The topology, line impedance data, data of each node, data of the phase-changing switch and SVG of the distribution network are obtained; based on the obtained topology, line impedance data, data of each node, data of the phase-changing switch and SVG, a multi-objective function for optimizing the voltage imbalance of all nodes in the distribution network and an optimization model for the phase sequence of the phase-changing switch and the compensation instruction current of the SVG are established; the three-phase unbalanced power flow is used to calculate the three-phase voltage of the node, and the obtained phase sequence of the phase-changing switch and the SVG compensation instruction current optimization model are optimized using a fast non-dominated sorting genetic algorithm to obtain the Pareto front solution set of the phase sequence optimization of the phase-changing switch and the negative-sequence compensation current of the SVG; the obtained Pareto front solution set is screened, and the result that meets the national standard and can reduce the number of phase changes of the phase-changing switch and the negative-sequence compensation current of the SVG is selected as the optimal instruction; according to the obtained optimal instruction, the phase-changing instruction and the compensation current instruction are respectively issued to the phase-changing switch and the SVG in the distribution network to realize the comprehensive management of the voltage imbalance of all nodes in the distribution network.

[0075] See also Figure 8 , the terminal device is a computer device, and the computer device 60 of this embodiment includes: a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable on the processor 61. When the computer program 63 is executed by the processor 61, the method for managing voltage imbalance in a distribution station area based on a phase-changing switch and SVG in the embodiment is implemented. To avoid repetition, it is not described one by one here. Alternatively, when the computer program 63 is executed by the processor 61, the functions of each model / unit in the system for managing voltage imbalance in a distribution station area based on a phase-changing switch and SVG in the embodiment are implemented. To avoid repetition, it is not described one by one here.

[0076] The computer device 60 may be a computing device such as a desktop computer, a notebook, a PDA, or a cloud server. The computer device 60 may include, but is not limited to, a processor 61 and a memory 62. Those skilled in the art will appreciate that Figure 8 This is only an example of the computer device 60 and does not constitute a limitation of the computer device 60. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the computer device may also include input and output devices, network access devices, buses, etc.

[0077] The processor 61 may be a central processing unit (CPU), or other general-purpose processors, graphics processing units (GPU), tensor processing units (TPU), digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or the processor may be any conventional processor, etc.

[0078] The memory 62 may be an internal storage unit of the computer device 60, such as a hard disk or memory of the computer device 60. The memory 62 may also be an external storage device of the computer device 60, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc., equipped on the computer device 60.

[0079] Furthermore, the memory 62 may include both an internal storage unit of the computer device 60 and an external storage device. The memory 62 is used to store computer programs and other programs and data required by the computer device. The memory 62 may also be used to temporarily store data that has been output or is to be output.

[0080] See also Fig. 9 The terminal device is an electronic device 600, which is in the form of a general-purpose computing device. The components of the electronic device may include, but are not limited to: at least one processing unit 610, at least one storage unit 620, a bus 630 connecting different platform components (including the storage unit 620 and the processing unit 610), a display unit 640, etc.

[0081] The storage unit stores program codes, which can be executed by the processing unit 610, so that the processing unit 610 performs the steps according to various exemplary embodiments of the present invention described in the above method section of this specification. For example, the processing unit 610 can perform the following steps: Figure 1 Follow the steps shown in .

[0082] The storage unit 620 may include a readable medium in the form of a volatile storage unit, such as a random access memory unit (RAM) 6201 and / or a cache memory unit 6202 , and may further include a read-only memory unit (ROM) 6203 .

[0083] The storage unit 620 may also include a program / utility 6204 having a set (at least one) of program modules 6205, such program modules 6205 including but not limited to: an operating system, one or more application programs, other program modules, and program data, each of which or some combination may include an implementation of a network environment.

[0084] Bus 630 may represent one or more of several types of bus structures, including a memory unit bus or memory unit controller, a peripheral bus, an accelerated graphics port, a processing unit, or a local bus using any of a variety of bus architectures.

[0085] The electronic device 600 may also communicate with one or more external devices 700 (e.g., keyboards, pointing devices, Bluetooth devices, etc.), may also communicate with one or more devices that enable a user to interact with the electronic device 600, and / or communicate with any device that enables the electronic device 600 to communicate with one or more other computing devices (e.g., routers, modems, etc.). Such communication may be performed via an input / output (I / O) interface 650. Furthermore, the electronic device 600 may also communicate with one or more networks (e.g., a local area network (LAN), a wide area network (WAN), and / or a public network, such as the Internet) via a network adapter 660. The network adapter 660 may communicate with other modules of the electronic device 600 via a bus 630. It should be understood that, although not shown in the figure, other hardware and / or software modules may be used in conjunction with the electronic device 600, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage platforms, etc.

[0086] Example 4 The present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a terminal device for storing programs and data. It is understandable that the computer-readable storage medium here can include both built-in storage media in the terminal device and extended storage media supported by the terminal device, and can be any tangible medium containing or storing a program, which can be used by an instruction execution system, device or device or used in combination with it. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by a processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that more specific examples (non-exhaustive list) of the computer-readable storage medium here include: an electrical connection with one or more wires, a portable disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0087] Computer readable storage media also include data signals propagated in baseband or as part of a carrier wave, which carry readable program codes. Such propagated data signals can take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. The readable storage medium can also be any readable medium other than a readable storage medium, which can send, propagate, or transmit a program for use by or in conjunction with an instruction execution system, device, or device. The program code contained on the readable storage medium can be transmitted using any appropriate medium, including but not limited to wireless, wired, optical cable, RF, etc., or any suitable combination of the above.

[0088] Program code for performing the operations of the present invention may be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java, C++, etc., and conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may be executed entirely on the user computing device, partially on the user device, as a separate software package, partially on the user computing device and partially on a remote computing device, or entirely on a remote computing device or server. In the case of a remote computing device, the remote computing device may be connected to the user computing device through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computing device (e.g., through the Internet using an Internet service provider).

[0089] The processor may load and execute one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the method for controlling voltage imbalance in a distribution station area based on a phase-changing switch and SVG in the above embodiment; the processor may load and execute the following steps of one or more instructions in the computer-readable storage medium: The topology, line impedance data, data of each node, data of the phase-changing switch and SVG of the distribution network are obtained; based on the obtained topology, line impedance data, data of each node, data of the phase-changing switch and SVG, a multi-objective function for optimizing the voltage imbalance of all nodes in the distribution network and an optimization model for the phase sequence of the phase-changing switch and the compensation instruction current of the SVG are established; the three-phase unbalanced power flow is used to calculate the three-phase voltage of the node, and the obtained phase sequence of the phase-changing switch and the SVG compensation instruction current optimization model are optimized using a fast non-dominated sorting genetic algorithm to obtain the Pareto front solution set of the phase sequence optimization of the phase-changing switch and the negative-sequence compensation current of the SVG; the obtained Pareto front solution set is screened, and the result that meets the national standard and can reduce the number of phase changes of the phase-changing switch and the negative-sequence compensation current of the SVG is selected as the optimal instruction; according to the obtained optimal instruction, the phase-changing instruction and the compensation current instruction are respectively issued to the phase-changing switch and the SVG in the distribution network to realize the comprehensive management of the voltage imbalance of all nodes in the distribution network.

[0090] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0091] In order to prove the correctness and effectiveness of this method, the full-node imbalance suppression effect of the proposed distribution network voltage imbalance management method is verified in combination with the attached drawings and simulation tests.

[0092] Figure 4 For a 15-node distribution network, 8 phase-changing switches are installed at nodes 3, 4, 7, 8, 10, 11, 12, and 13, and 2 SVGs are installed at nodes 2 and 11. A large number of single-phase loads are connected to the nodes in the system, and there is a serious voltage imbalance at the nodes in the system.

[0093] The initial phase sequence of the commutation switch is shown in Table 1: Table 1

[0094] Figure 5 The figure shows the negative sequence voltage imbalance of each node in the local distribution network before treatment. According to national standards, the negative sequence voltage imbalance is less than 2% during normal operation of the power grid. As shown in the figure, each node in the system has a high negative sequence voltage imbalance, with the highest being close to 10%, far exceeding the national standard.

[0095] As mentioned above, the phase sequence of the phase-changing switch and the negative sequence current output by SVG are optimized based on the NSGA-II algorithm. The sum of the negative sequence voltage imbalance of all nodes, the minimum number of phase-changing switches and the minimum output compensation current capacity of SVG are used as the objective functions to calculate the Pareto optimal solution set of the phase sequence of the phase-changing switch and the negative sequence current output by SVG. It can be seen from the figure that when the number of switching times of the phase-changing switch is 0, that is, when the phase-changing switches are not in action, the two installed SVGs can manage the voltage imbalance of all nodes in the system to a certain extent, but it cannot guarantee that the voltage imbalance of all nodes meets the national standards. With the increase in the number of phase-changing switch actions, the voltage imbalance of the system after management has a decreasing trend, and the required total output current capacity of SVG is reduced under the same management effect, and a feasible solution that meets the national standards appears.

[0096] The optimal compromise solution with a smaller number of commutation switches and a smaller total negative sequence current capacity of SVG is selected from the feasible solutions. The solution with a commutation number of 3 can be selected. The switching phase sequence of the commutation switches is shown in Table 2, and the SVG output negative sequence current is shown in Table 3.

[0097] Table 2

[0098] Table 3

[0099] Figure 7 The voltage imbalance of each node in the system is controlled. As shown in the figure, the negative sequence voltage imbalance of each node is reduced to below the national standard. This result verifies the economy and feasibility of the control method proposed in the present invention.

[0100] In summary, the present invention provides a method and system for controlling voltage imbalance in a distribution station area based on phase-changing switches and SVG. The voltage imbalance of all nodes in the distribution network is used as the control target, and the three-phase imbalance of the negative-sequence voltage of the distribution network is used as the control target. Compared with the traditional phase-changing switch control scheme, the voltage imbalance of all nodes can be suppressed, and it is not limited to the suppression of the current imbalance on the low-voltage side of the transformer. The imbalance calculated using the three-phase unbalanced power flow takes into account the voltage amplitude and phase, and can better reflect the actual operating status of the distribution network. By optimizing the phase sequence of the phase-changing switches in the distribution network and the negative-sequence output current of SVG, the comprehensive control of the voltage imbalance of all nodes in the distribution network can be achieved, which can not only control the imbalance from the load side, but also combine the advantages of active compensation and fine compensation.

[0101] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0102] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0103] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in the present invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0104] In the embodiments provided by the present invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are only schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0105] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0106] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0107] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electric carrier signals and telecommunication signals.

[0108] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices, and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0109] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0110] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0111] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for controlling voltage imbalance in a distribution station area based on phase-changing switches and SVG, characterized in that: The following steps are involved: S1. Obtain the topology of the distribution network, line impedance data, data of each node, phase-changing switch and SVG data; S2. According to the topology of the distribution network, the line impedance data, the data of each node, the phase-changing switch and the SVG data obtained in step S1, a multi-objective function for optimizing the voltage imbalance of all nodes in the distribution network and an optimization model for the phase sequence of the phase-changing switch and the SVG compensation instruction current are established; S3, using the three-phase unbalanced power flow to calculate the node three-phase voltage, using the fast non-dominated sorting genetic algorithm to optimize the commutation switch phase sequence and SVG compensation command current optimization model obtained in step S2, and obtain the Pareto frontier solution set of the commutation switch phase sequence optimization and SVG negative sequence compensation current; S4, screening the Pareto front solution set obtained in step S3, and selecting the result that not only meets the national standard but also reduces the number of commutation times of the commutation switch and the negative sequence compensation current of the SVG as the optimal instruction; S5. According to the optimal instruction obtained in step S4, a commutation instruction and a compensation current instruction are respectively issued to the commutation switches and SVG in the distribution network to achieve comprehensive management of voltage imbalance at all nodes in the distribution network.

2. The method for controlling voltage imbalance in a distribution station area based on phase-changing switches and SVG according to claim 1 is characterized in that: In step S1, the distribution network topology includes the three-phase topology of the network; the three-phase line impedance data includes the three-phase line impedance of the adjacent nodes; the data of each node includes the load power of each node, the voltage amplitude and phase angle data of each node; the phase-changing switch data includes the current phase-changing switch access phase sequence; the SVG data includes the rated capacity of each SVG and the current output negative sequence current; form Order positive sequence, negative sequence, zero sequence node admittance matrix , , .

3. The method for controlling voltage imbalance in a distribution station area based on phase-changing switches and SVG according to claim 1 is characterized in that: Step S2 is specifically as follows: S201. Determine that the target of comprehensive management of three-phase imbalance in the distribution network is that the negative sequence voltage imbalance of each node is less than 2%; S202. Construct a multi-objective function for optimizing voltage imbalance at all nodes of the distribution network and an optimization model for the phase sequence of the commutation switch and the SVG compensation instruction current, with the optimization objectives of minimizing the sum of the negative sequence voltage imbalance at all nodes, minimizing the number of commutation times, and minimizing the sum of the negative sequence compensation current amplitudes output by SVG; the constraints include that the three-phase voltage at the distribution network node is maintained within the range specified by the national standard, the number of continuous actions of a single commutation switch does not exceed the specified upper limit, and the negative sequence current output by SVG does not exceed the rated capacity; The controlled variables are the phase sequence of the commutation switch and the negative sequence compensation current output by the SVG.

4. The method for controlling voltage imbalance in a distribution station area based on a phase-changing switch and SVG according to claim 3 is characterized in that: The multi-objective function for optimizing voltage imbalance at all nodes in the distribution network includes: Total negative sequence voltage unbalance objective function: in, is the node number, is the number of network nodes, For Node The negative sequence voltage unbalance degree, For Node m The negative sequence voltage, For Node m The positive sequence voltage; SVG total output capacity objective function: in, k Number the SVG. K is the total number of SVGs, is the output negative sequence current of the kth SVG; Commutation times objective function: in, It is the total number of commutation times of the commutation switch compared to the current phase sequence.

5. The method for controlling voltage imbalance in a distribution station area based on phase-changing switches and SVG according to claim 3 is characterized in that: The node voltage constraints are as follows: in, is the minimum node voltage, is the maximum node voltage; Each phase-changing switch sets a maximum number of continuous phase-changing times. If a phase-changing switch operates continuously for more than the specified value, the current phase sequence will remain unchanged during the next phase-changing. The action constraints are as follows: in, For the p The number of consecutive commutation times of a commutation switch, For the p The maximum number of continuous commutation times of a phase-changing switch.

6. The method for controlling voltage imbalance in a distribution station area based on phase-changing switches and SVG according to claim 1 is characterized in that: In step S3, the three-phase unbalanced power flow and the fast non-dominated sorting genetic algorithm NSGA-II are applied to solve the multi-objective optimization model, and the multi-node voltage unbalance optimization model and the three objective functions of the model are solved; through multiple iterative optimizations of the fast non-dominated genetic algorithm (NSGA-Ⅱ), a set of Pareto optimal solution sets are obtained, and the objective function of the Pareto optimal solution set is equivalent to the Pareto optimal frontier of total negative sequence voltage imbalance, number of commutation times and total output capacity of SVG.

7. The method for controlling voltage imbalance in a distribution station area based on phase-changing switches and SVG according to claim 6 is characterized in that: The NSGA-Ⅱ algorithm is used to solve the multi-objective optimization problem established in step S2 as follows: S3021, generating an initial population of the genetic algorithm, the population size is POP, and a single individual includes the phase sequence of the phase-changing switch and the negative sequence current output by the SVG; S3022, calculating three individual objective functions, the total voltage unbalance objective function needs to be obtained through the unbalanced power flow calculation result; S3023, non-dominated sorting and crowding analysis, non-dominated sorting and crowding calculation are performed on all individuals in the population, and the priority and ranking of the individuals in the population are determined through the three fitness functions of the individuals; Secondly, the crowding degree is calculated and individuals at the same level are sorted to prevent the algorithm solution from falling into the local optimum; retaining individuals with high crowding degree is conducive to population diversity; S3024. Selecting parents suitable for reproduction based on the tournament selection method and placing them into a mating pool, wherein the number of individuals in the mating pool is half of the initial population; S3025. Randomly select a parent generation in the mating pool, perform crossover and genetic operations, and generate offspring individuals; S3026, merge the parent population and the child population to obtain a merged population, perform non-dominated sorting and crowding calculation on the merged population based on the elite selection strategy, and generate a new population with the top-ranked POP individuals; S3027. Determine whether to stop iteration based on the objective function of each individual in the new population, the number of iterations and other convergence conditions. If iteration is not stopped, perform selection, crossover and mutation operations on the population to generate the next generation population and enter step S302. If the convergence conditions are met, output the Pareto optimal solution set.

8. The method for controlling voltage imbalance in a distribution station area based on phase-changing switches and SVG according to claim 7 is characterized in that: In step S3021, the total voltage unbalance objective function is obtained through the unbalanced power flow calculation result, which is as follows: S30221, set the initial value of node positive sequence, negative sequence and zero sequence voltage , , , the positive sequence voltage amplitude is 1.0pu, the negative sequence and zero sequence voltage amplitudes are 0, and the initial values ​​of the node three-phase voltages are calculated , , ; S30222, based on node injection power , , , update the node injection three-phase current, and based on the symmetrical component method, calculate the node injection positive sequence, negative sequence, and zero sequence current in the updated network , , ; S30223, the positive sequence network is an active network, and the forward-backward substitution method is used to solve the node positive sequence voltage , the negative sequence network and the zero sequence network are passive networks, and the node voltage equation is used to obtain , , t is the number of iterations; S30224, generate node three-phase voltage , , ; S30225, determine whether it has converged or reached the maximum number of iterations, if not converged or not reached the maximum number of iterations, update t= t+ 1. Start the next iteration from step S30222.

9. The method for controlling voltage imbalance in a distribution station area based on phase-changing switches and SVG according to claim 1, characterized in that: In step S4, firstly, the feasible solutions that meet the standards in the Pareto optimal solution set obtained in step S3 are screened, and after taking the commutation switch phase sequence optimization instructions and the SVG output negative sequence current instructions represented by the feasible solutions, the voltage imbalance degree of all nodes in the local distribution network meets the national standard requirements; Then, a non-dominated sorting is completed again among the remaining feasible solutions, and the optimal compromise solution with low commutation times and small total SVG output capacity is selected as the commutation switch phase sequence optimization instruction and SVG output negative sequence current instruction.

10. A voltage imbalance management system for distribution station area based on phase-changing switches and SVG, characterized in that: include: Data module, which obtains the topology of the distribution network, line impedance data, data of each node, phase-changing switch and SVG data; The construction module establishes a multi-objective function for optimizing voltage imbalance at all nodes of the distribution network and an optimization model for the phase sequence of the commutation switch and the compensation command current of the SVG based on the obtained distribution network topology, line impedance data, data of each node, commutation switch and SVG data; The optimization module uses the three-phase unbalanced power flow to calculate the three-phase voltage of the node, and uses the fast non-dominated sorting genetic algorithm to optimize the obtained commutation switch phase sequence and SVG compensation command current optimization model to obtain the Pareto frontier solution set of the commutation switch phase sequence optimization and SVG negative sequence compensation current; The screening module screens the obtained Pareto front solution set and selects the result that not only meets the national standard but also reduces the number of commutation switches and the negative sequence compensation current of SVG as the optimal instruction; The output module, based on the obtained optimal instructions, sends commutation instructions and compensation current instructions to the commutation switches and SVG in the distribution network respectively, to achieve comprehensive management of voltage imbalance at all nodes in the distribution network.

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